Armando Dias Tavares

Structural and vibrational study of chromium doped elpasolite crystals Cs2NaAlF6

The influence of site-symmetry and electron phonon coupling in Cs2NaAlF6:Cr3+ is probed by correlation of optical and structural measurements. Based on neutron and x-ray analysis the structure is a distorted R3m¯, exhibiting a unique stacking interaction. Selection rules have been used to assign the Raman-active zone-center vibrations. Although local and bulk mode frequencies differ slightly, indicating that the guest Cr3+ ion does not significantly perturb the host structure, vibrational analysis indicates the Cr3+ ion is coupled to the first coordination sphere of the Al–F lattice.

Laboratory teaching in optics: formation x information and the physics and engineering students

The way laboratory work should be conducted and the effectiveness of the two major usual approaches for doing that are discussed. The mapping of problems presented by both these methods is discussed in the context of their application in the Education of physicists and engineers at undergraduate level. The challenges posed by trying to teach as much as possible, in as little as possible time, for as much as possible people are analyzed and some solutions are proposed.